Technical Field
The embodiments herein generally relate to a junction gate field-effect transistor, and, more particularly, configuring a junction gate field-effect transistor (JFT) with a bipolar junction transistor (BJT) for a logic driven device with automatic compensation of beta variation and to reduce a chip area of a circuit.
Description of the Related Art
Bipolar junction transistors are one of the many power devices. The bipolar junction transistors are used as Darlington pairs, low Vice (sat) bipolar junction transistors and/or high beta transistors. Since bipolar junction transistors are current driven devices, resistors are necessarily connected to the base of the bipolar junction transistors to control base current. In the bipolar junction transistors, a collector gets a bias through a load, and a base gets a bias through the resistor connected to the base to control the current. FIG. 1 is a typical circuit diagram that illustrates resistors configured with bipolar junction transistors in a Darlington pair configuration. The circuit diagram 100 includes resistors 102A-C, bipolar junction transistors 104A-B. The resistors 102A-C are base current controlling resistors. The resistors 102A-C are used to interface a logic signal driver used in peripheral devices such as (a) a stepper motor, (b) relays, (c) bulbs, (d) LEDs, (e) print head hammers, and (f) brushless DC motors. The peripheral devices are characterized by (a) high voltage (i.e. 50-100 volts), (b) high current (i.e. 500 mA peak to several amperes), and (c) Often inductive. In the circuit 100, different source voltages are addressed, when a separate device is provided for each voltage range. For example, the resistors 102A-C are integrated into a monolithic integrated circuit. Hence, the resistors 102A-C required in the Darlington pair configuration to address the base current control sources with different input voltage ranges. In one embodiment, the resistors are 2.7 kilo ohms or 10.5 kilo ohms. The bipolar junction transistors 104A-B are involved in the Darlington pair configuration. In the Darlington pair configuration, an equivalent base current of the transistor 104A is amplified and becomes the base current of transistor 104B. When the base of the transistor 104A is open, a collector to emitter current equal to beta times a leakage current from collector to base current of transistor 104A flows into the base of 104B. The emitter current becomes the base current of the transistor 104B and hence large load current can flow. This load current can lead to faulty operation and large power dissipation. In order to avoid the large load current flow, large number of resistors (e.g., the resistors 102A-C) is provided in the Darlington pair configuration. Hence, the chip area of the Darlington pair configuration is high. Accordingly there remains need for providing a logic driven device with better compensation of beta variation and to reduce a chip area of a circuit.